1. Field of the Invention
This invention relates to a gas detecting device principally for detecting liquor contained in expired gas of a vehicle operator.
2. Description of the Prior Art
A gas detecting device of the type wherein expired gas of a driver of a car such as an automobile or a motorcycle is positively taken in and an indicator lamp is controlled to be lit up by a detecting circuit in response to a change in electric conductivity of a gas detecting element made of a semiconductor and provided in the detecting circuit in accordance with a well known semiconductor characteristic reaction of the detecting element itself when the expired gas taken into the device is contacted with the gas detecting element in order to facilitate detection of liquor present in the expired gas taken into the device, is disclosed, for example, in Japanese Publication Utility Model No. 52-35759.
According to the gas detecting device, a volume in the detecting circuit is adjusted, prior to forwarding or shipment of the device, at an inspection stage of production steps such that the indicator lamp may be lit up when the device is positioned at a point spaced a predetermined distance (normally at a point spaced by a distance from 15 to 20 cm) from test alcohol of a predetermined fixed concentration.
Accordingly, it is desirable that the gas detecting device is spaced, in actual use thereof, by such a distance as described above from a mouth of an object person for measurement who is a driver of a car.
However, the gas detecting device is used, in most cases, particularly outdoors at night, and actually a measurer holds the gas detecting device in one hand and an illuminating device such as a flash-light in the other hand to illuminate a mouth of an object person for measurement in order to set a distance to the gas detecting device. According to the gas detecting device, if measurement is not accomplished at a position of the aforementioned predetermined distance, the sensitivity of the detecting element will vary accordingly, resulting in possible errors in measurement. Thus, it is troublesome for the measurer to make measurement while he holds a gas detecting device and an illuminating device in both hands, and it is difficult for him to always make accurate measurement since both hands are occupied.
Meanwhile, setting of the distance from an object person for measurement and the gas detecting device must rely upon eye measurement of a measurer. Consequently, a difference in setting of a distance will vary the sensitivity of the gas detecting element, resulting in possible errors in measurement, and thus setting of a distance is troublesome to a measurer who must always attain accurate measurement.
In addition, since the gas detecting device must necessarily be used in an appropriate atmosphere, for example, to remove deviations of operating characteristics caused by the temperature in order to attain stabilized measurement, generally a heater within the detecting element of the gas detecting device is energized so that the gas detecting device may be operated at a relatively high temperature. Accordingly, the heater normally requires a relatively large electric current, and hence exhaustion of a power source at an early stage cannot be avoided by large power consumption. Since such gas detecting devices are used for a long time particularly outdoors at night, in most cases they are of the portable type and employ dry cells as a power source. Accordingly, large power consumption is required for heating with a heater and hence will cause exhaustion of such cells at an early stage so that before such exhaustion of cells is noticed, measurement may possibly be performed. Thus, the gas detecting device is disadvantageous in its reliability.